1. Field of the Invention
The present invention relates generally to computer drawing programs, and in particular, to a method, apparatus, and article of manufacture for displaying a visual indicator that indicates potential object manipulations in the computer drawing program.
2. Description of the Related Art
Computer-implemented graphics systems have been widely used by designers, illustrators, drafters, and engineers for a number of years. Most such graphics systems use a two-dimensional (2D) graphical user interface (GUI) to display graphical images, such as 2D or three-dimensional (3D) models, schematic diagrams, photorealistic images, etc.
Subsequent to placement of a graphical object in a drawing, a user often manipulates the graphical object (e.g., by resizing, rotating, stretching/expanding, shortening, etc.). To assist in a manipulation, the system may provide for the use of a glyph or a grip. A glyph is a symbol that conveys information non-verbally. A grip is a glyph that has a defined position and an active area within which a pointing device will “snap” to that position. To manipulate the system, a user selects the grip or glyph and drags the cursor in a desired direction. The underlying graphical object is then manipulated based on the grip limitations and the drag operation.
Grip glyphs have been used extensively in two-dimensional graphic editing, and more recently in three-dimensional model editing. However, in prior art techniques, a user must determine from the position of a grip glyph what a resulting action will be. Thereafter, the user must determine a valid direction constraint, usually by experimentation. FIG. 1 illustrates grip glyphs as used in the prior art. As illustrated, a door graphical image/object 100 has numerous square grip glyphs 102-108. The user must first guess and then experiment to determine what each grip 102-108 does and how the grip 102-108 may be used based on the grip's 102-108 location within door object 100. For example, since grip 102 and 106 are in corner positions, the user may guess and then experiment to determine that grips 102 and 106 may be used to change the width (and maybe the height) of door object 100. Further, since grips 104 and 108 are located in the middle of door object 100, the user may guess and experiment to determine that grip 104 may be used to change the location and grip 108 may be used to change the opening angle of door object 100, and since grips 110 and 112 are located at the top corners of door object 100, the user may guess and experiment to determine that grips 110 and 112 may be used to change the height of door object 100.
Thus, as illustrated in FIG. 1, the prior art square grip glyphs 102-108 do not provide sufficient information to enable a user to quickly (and without experimentation) determine which grip glyph 102-108 to use to accomplish a desired task.
In data visualization fields, glyphs may be oriented to provide a visual indicator for the user. For example, an oriented glyph may be used in data visualization to graphically indicate data values, such as an arrow indicating wind direction on a two-dimensional field or blood flow through an artery. However, oriented glyphs have not been used to assist a user in interacting with and manipulating an image in three dimensions.